LAS Glass Refining with Tin Oxide at Moderate Temperatures
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Solution Overview
Problem
The existing methods for refining glass melts for glass-ceramic production are costly and inefficient due to the need for high-temperature refining units and high refining agent contents, which lead to increased energy consumption and the risk of component evaporation, while also resulting in a high number of bubbles in the glass and ceramic products.
Innovation Solution
A process for refining a lithium aluminum silicate (LAS) glass melt using tin oxide as a refining agent with a content of ≤0.4% by weight, optimizing the melting tank design to minimize residence time and average glass temperature, allowing for refining at temperatures below 1700°C without additional high-temperature units, thereby reducing bubble formation to <1 bubble/kg melt.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high-temperature refining units are used to refine glass melt, then bubble removal is improved, but energy consumption increases and production costs increase
Solution Approach 1:
The patent changes the temperature parameter from conventional high temperatures (>1750°C) to moderate temperatures (1600-1720°C), and adjusts the refining agent content parameter to optimize the refining process. This parameter change resolves the contradiction by achieving effective bubble removal at lower temperatures, thus reducing energy consumption while maintaining manufacturing precision.
Solution Approach 2:
The patent uses moderate amounts of refining agents (≤0.4% by weight of tin oxide, or combinations with antimony and/or arsenic oxides) that perform their refining function and are then consumed or removed, avoiding the need for expensive, complex high-temperature refining units while achieving the desired bubble quality.
2Speed
If high refining agent contents are used to increase bubble diameter and rise rate, then bubble removal is improved, but batch costs increase and evaporation problems occur
Solution Approach 1:
The patent optimizes the refining agent content parameter to moderate levels (≤0.4% by weight for tin oxide alone, or up to 0.5% when combined with antimony and/or arsenic oxides), which is sufficient to generate gas bubbles that rise at an adequate rate without causing excessive batch costs or evaporation problems during hot forming.
Solution Approach 2:
The patent combines multiple refining agents (tin oxide with antimony and/or arsenic oxides) in specific proportions to achieve the desired bubble rise rate, effectively using a composite approach that reduces the total refining agent content needed while maintaining the speed of bubble removal.
3Productivity
If high temperatures are used during refining, then bubble growth and rise is accelerated, but component evaporation from the glass melt increases
Solution Approach 1:
The patent changes the temperature parameter from conventional high temperatures (>1750°C) to moderate temperatures (1600-1720°C), which maintains adequate refining speed through the use of optimized refining agent combinations while significantly reducing component evaporation losses from the glass melt.
4Manufacturing precision
If additional high-temperature refining units are installed, then bubble removal is improved, but investment costs and device complexity increase
Solution Approach 1:
The patent extracts the refining function from separate, complex high-temperature refining units and integrates it into the main melting tank through the use of moderate-temperature refining with optimized refining agent combinations, thereby simplifying the overall device configuration while maintaining manufacturing precision.
Solution Approach 2:
The patent makes the main melting tank perform both melting and refining functions at moderate temperatures through the use of refining agents, eliminating the need for separate specialized refining units and reducing device complexity while achieving the desired bubble quality.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach achieves high bubble quality in green glass and glass ceramic products with moderate refining agent content, reducing production costs and energy consumption while maintaining low bubble counts, as demonstrated by tank tests and mathematical simulations.
Implementation Method 1
Due to their static buoyancy due to the difference in density between the gas bubbles and the glass melt, the gas bubbles naturally tend to rise in the melt and then escape into the open.
Implementation Method 2
The bubbles grow or shrink when the pressure inside the bubble is higher or lower than the equilibrium pressure of the dissolved gases.
Implementation Method 3
the dissolved gases spontaneously form new bubbles on so-called germs (walls, mini-bubbles), which usually leads to foam
Data Source
Figure 1~2
Figure 3
Figure 4A~4B
AI summary
According to the prior art, the production of green glass for a LAS glass-ceramic with sufficiently low bubble counts requires either high concentrations of polyvalent refining agents or tin oxide (> 0.5 wt%) at high melting/refining temperatures > 1600°C or very high refining temperatures (> 1750°C) with moderate refining agents (< 0.25 wt%). Both options entail a number of serious disadvantages for the manufacturing process, the environment, and/or economic viability. To avoid these disadvantages, the invention provides a method for refining a glass melt for a glass-ceramic green glass with the following steps and a correspondingly designed melting furnace: - Providing a glass mixture based on a lithium aluminum silicate (LAS) glass system with the sole addition of tin oxide as a refining agent at a concentration < 0.4 wt.-% without arsenic and/or antimony oxide as refining agent, - Design of the melting furnace with regard to minimum residence time of the glass to be refined and mean glass temperature according to the formula: tminT,x=2+0.5⋅1700-Tmit+50⋅0.40-xh for Tmit≤1700°C and x≤0.40%mit Tmit=mean glass temperature;x=refining agent content, tmin=minimum residence time, and - Melting of the batch and refining of the melt at temperatures < 1700°C without additional special high-temperature refining units.